Method for predicting a fault in an air-conditioning pack of an aircraft

ABSTRACT

A method of predicting a fault in an air-conditioning pack of an aircraft is disclosed. The air-conditioning pack includes one or more sensors outputting data related to air-conditioning pack temperature, air-conditioning pack pressure, or air-conditioning pack valve or actuator positions. The method includes transmitting data from at least one of the sensors operably coupled to the air-conditioning pack, comparing the transmitted data to a predetermined threshold, and predicting a fault in the air-conditioning pack based thereon.

BACKGROUND

Contemporary aircrafts include air-conditioning systems that take hotair from the engines of the aircraft for use within the aircraft.Currently, airlines and maintenance personnel wait until a fault orproblem occurs with the system and then attempt to identify the causeand fix it during either scheduled or, more likely, unscheduledmaintenance. Fault occurrences are also recorded manually based on pilotdiscretion.

BRIEF DESCRIPTION

Embodiments generally relate to a method of predicting a fault in anair-conditioning pack of an aircraft where the air-conditioning packincludes one or more sensors, including transmitting data from at leastone of the sensors operably coupled to the air-conditioning pack,comparing the transmitted data to a predetermined threshold, predictinga fault in the air-conditioning pack based on the comparison, andproviding an indication of the predicted fault.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of an aircraft and a ground system in whichembodiments may be implemented;

FIG. 2 is a schematic view of a portion of an exemplary air-conditioningsystem;

FIG. 3 is a schematic view of a portion of an exemplary air-conditioningsystem; and

FIG. 4 is a flowchart showing a method of predicting a fault in anair-conditioning pack according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates an aircraft 8 that may include an air-conditioningsystem 10, only a portion of which has been illustrated for claritypurposes, and may execute embodiments. As illustrated, the aircraft 8may include multiple engines 12 coupled to a fuselage 14, a cockpit 16positioned in the fuselage 14, and wing assemblies 18 extending outwardfrom the fuselage 14. While a commercial aircraft has been illustrated,embodiments may be used in any type of aircraft, for example, withoutlimitation, fixed-wing, rotating-wing, rocket, personal aircraft, andmilitary aircraft. Further, while two engines 12 have been illustratedon each wing assembly 18, it will be understood that any number ofengines 12 including a single engine 12 may be included.

The air-conditioning system 10 may form a portion of the environmentalcontrol system of the aircraft 8 and may include a variety ofsubsystems. For example, among others, a bleed air system 20, one ormore air-conditioning packs 22, and an air distribution or cabintemperature control system 24 (FIG. 3) may be included in theair-conditioning system 10. The bleed air system 20 may be connected toeach of the engines 12 and air may be supplied to the air-conditioningsystem 10 by being bled from a compressor stage of each engine 12,upstream of the combustor. Various bleed ports may be connected tovarious portions of the engine 12 to provide highly compressed air tothe bleed air system 20. The temperature and pressure of this bleed airvaries widely depending upon which compressor stage and the RPM of theengine 12. The air-conditioning packs 22 and cabin temperature controlsystem 24 will be described in more detail with respect to FIGS. 2 and 3below.

A plurality of additional aircraft systems 30 that enable properoperation of the aircraft 8 may also be included in the aircraft 8. Anumber of sensors 32 related to the air-conditioning system 10, itssubsystems, and the additional aircraft systems 30 may also be includedin the aircraft 8. It will be understood that any number of sensors maybe included and that any suitable type of sensors may be included. Thesensors 32 may transmit various output signals and information.

A controller 34 and a communication system having a wirelesscommunication link 35 may also be included in the aircraft 8. Thecontroller 34 may be operably coupled to the air-conditioning system 10,the plurality of aircraft systems 30, as well as the sensors 32. Thecontroller 34 may also be connected with other controllers of theaircraft 8. The controller 34 may include memory 36, the memory 36 mayinclude random access memory (RAM), read-only memory (ROM), flashmemory, or one or more different types of portable electronic memory,such as discs, DVDs, CD-ROMs, etc., or any suitable combination of thesetypes of memory. The controller 34 may include one or more processors38, which may be running any suitable programs. The controller 34 may bea portion of an FMS or may be operably coupled to the FMS.

A computer searchable database of information may be stored in thememory 36 and accessible by the processor 38. The processor 38 may run aset of executable instructions to display the database or access thedatabase. Alternatively, the controller 34 may be operably coupled to adatabase of information. For example, such a database may be stored onan alternative computer or controller. It will be understood that thedatabase may be any suitable database, including a single databasehaving multiple sets of data, multiple discrete databases linkedtogether, or even a simple table of data. In an embodiment, the databasemay incorporate a number of databases or the database may actually be anumber of separate databases. The database may store data that mayinclude historical air-conditioning system data for the aircraft 8 andrelated to a fleet of aircraft. The database may also include referencevalues including predetermined threshold values, historic values, oraggregated values and data related to determining such values.

Alternatively, in an embodiment, the database may be separate from thecontroller 34 but may be in communication with the controller 34 suchthat it may be accessed by the controller 34. For example, the databasemay be contained on a portable memory device and in such a case, theaircraft 8 may include a port for receiving the portable memory deviceand such a port would be in electronic communication with controller 34such that controller 34 may be able to read the contents of the portablememory device. It is also possible that the database may be updatedthrough the wireless communication link 35 and that in this manner, realtime information may be included in the database and may be accessed bythe controller 34.

Further, in an embodiment, such a database may be located off theaircraft 8 at a location such as an airline operation center, flightoperations department control, or another location. The controller 34may be operably coupled to a wireless network over which the databaseinformation may be provided to the controller 34.

While a commercial aircraft has been illustrated, portions of theembodiments may be implemented anywhere including in a computer orcontroller 60 at a ground system 62. Furthermore, the database(s) asdescribed above may also be located in a destination server or acontroller 60, which may be located at and include the designated groundsystem 62. Alternatively, the database may be located at an alternativeground location. The ground system 62 may communicate with other devicesincluding the controller 34 and databases located remote from thecontroller 60 via a wireless communication link 64. The ground system 62may be any type of communicating ground system 62 such as an airlinecontrol or flight operations department.

FIG. 2 illustrates an exemplary schematic view of a cold air unit alsoknown as an air-conditioning pack 22 having a main heat exchanger 70, aprimary heat exchanger 72, compressor 73, a flow control valve 74, aturbine 75, an anti-ice valve 76, a ram air actuator 77, and acontroller 78, which may be located within the cockpit 16 of theaircraft 8 and may be operably coupled to the controller 34. It will beunderstood that additional components may also be included and that theabove is merely an example. Further, a number of sensors 32 have beenillustrated as being included within the air-conditioning pack 22. Thesensors 32 may output a variety of data including data related totemperatures of the air-conditioning pack 22, pressures of theair-conditioning pack 22, or valve positions. For example, some of thesensors 32 may output various parameters including binary flags forindicating valve settings and/or positions including for example thestate of the valve (e.g. fully open, open, in transition, close, fullyclosed).

It will be understood that any suitable components may be included inthe air-conditioning pack 22 such that it may act as a cooling device.The quantity of bleed air flowing to the air-conditioning pack 22 isregulated by the flow control valve 74. The bleed air enters the primaryheat exchanger 72 where it is cooled by either ram air, expansion, or acombination of both. The cold air then enters the compressor 73, whereit is re-pressurized, which reheats the air. A pass through the mainheat exchanger 70 cools the air while maintaining the high pressure. Theair then passes through the turbine 75, which expands the air to furtherreduce heat.

FIG. 3 illustrates an exemplary diagram of a cabin temperature controlsystem 24 having a mixer unit 80, recirculation fans 82, a manifold 84,and nozzles 86 that distribute air into zones 88 within the cabin 89 ofthe aircraft 8, as well as a control mechanism 90. As illustrated,exhaust air from the air-conditioning packs 22 may be mixed in a mixerunit 80 with filtered air from the recirculation fans 82 and fed into amanifold 84. Air from the manifold 84 may be directed to overheaddistribution nozzles 86 in the various zones 88 of the aircraft 8. Acontrol mechanism 90 may control the temperature in each zone 88 as wellas a variety of other aspects of the cabin temperature control system24. It will be understood that the control mechanism may be operablycoupled to the controller 34. A number of sensors 32 may be included andmay output signals related to various aspects of the cabin temperaturecontrol system 24 including temperatures within the zones 88, pressureswithin the cabin temperature control system 24, etc.

It will be understood that the aircraft 8 and the controller 60 merelyrepresent two exemplary embodiments that may be configured to implementembodiments or portions of embodiments. During operation, either theaircraft 8 and/or the controller 60 may predict a fault with theair-conditioning system 10 or a subsystem thereof. By way ofnon-limiting example, one or more sensors 32 may transmit data relevantto various characteristics of the air-conditioning system 10. Thecontroller 34 and/or the controller 60 may utilize inputs from thecontrol mechanisms, sensors 32, aircraft systems 30, the database(s),and/or information from airline control or flight operations departmentto predict the fault with the air-conditioning system 10 or a subsystemthereof. Among other things, the controller 34 and/or the controller 60may analyze the data over time to determine drifts, trends, steps, orspikes in the operation of the air-conditioning system 10. Thecontroller 34 and/or the controller 60 may also analyze the sensor dataand predict faults in the air-conditioning system 10 based thereon. Oncea fault with the air-conditioning system 10 or a subsystem thereof hasbeen predicted an indication may be provided on the aircraft 8 and/or atthe ground system 62. In an embodiment, the diagnosis of the fault withthe air-conditioning system 10 or a subsystem thereof may be done duringflight, may be done post flight, or may be done after any number offlights. The wireless communication link 35 and the wirelesscommunication link 64 may both be utilized to transmit data such thatthe fault may be predicted by the controller 34 and/or the controller60.

One of the controller 34 and the controller 60 may include all or aportion of a computer program having an executable instruction set forpredicting an air-conditioning pack fault in the aircraft 8. Suchpredicted faults may include improper operation of components as well asfailure of components. As used herein the term prediction refers to aforward-looking determination that makes the fault known in advance ofwhen the fault occurs and contrasts with detecting or diagnosing, whichrefers to a determination after the fault has occurred. Along withpredicting the controller 34 and/or the controller 60 may detect thefault. Regardless of whether the controller 34 and/or the controller 60runs the program for predicting the fault, the program may include acomputer program product that may include machine-readable media forcarrying or having machine-executable instructions or data structuresstored thereon.

It will be understood that details of environments that may implementembodiments are set forth in order to provide a thorough understandingof the technology described herein. It will be evident to one skilled inthe art, however, that the exemplary embodiments may be practicedwithout these specific details. The exemplary embodiments are describedwith reference to the drawings. These drawings illustrate certaindetails of specific embodiments that implement a module or method, orcomputer program product described herein. However, the drawings shouldnot be construed as imposing any limitations that may be present in thedrawings. The method and computer program product may be provided on anymachine-readable media for accomplishing their operations. Theembodiments may be implemented using an existing computer processor, orby a special purpose computer processor incorporated for this or anotherpurpose, or by a hardwired system. Further, multiple computers orprocessors may be utilized including that the controller 34 and/or thecontroller 60 may be formed from multiple controllers. It will beunderstood that the controller predicting the fault may be any suitablecontroller including that the controller may include multiplecontrollers that communicate with each other.

As noted above, embodiments described herein may include a computerprogram product comprising machine-readable media for carrying or havingmachine-executable instructions or data structures stored thereon. Suchmachine-readable media may be any available media, which may be accessedby a general purpose or special purpose computer or other machine with aprocessor. By way of example, such machine-readable media can compriseRAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any other medium thatcan be used to carry or store desired program codes in the form ofmachine-executable instructions or data structures and that can beaccessed by a general purpose or special purpose computer or othermachine with a processor. When information is transferred or providedover a network or another communication connection (either hardwired,wireless, or a combination of hardwired or wireless) to a machine, themachine properly views the connection as a machine-readable medium.Thus, any such connection is properly termed a machine-readable medium.Combinations of the above are also included within the scope ofmachine-readable media. Machine-executable instructions comprise, forexample, instructions and data, which cause a general-purpose computer,special purpose computer, or special purpose processing machines toperform a certain function or group of functions.

Embodiments will be described in the general context of method stepsthat may be implemented in one embodiment by a program product includingmachine-executable instructions, such as program codes, for example, inthe form of program modules executed by machines in networkedenvironments. Generally, program modules include routines, programs,objects, components, data structures, etc. that have the technicaleffect of performing particular tasks or implement particular abstractdata types. Machine-executable instructions, associated data structures,and program modules represent examples of program codes for executingsteps of the method disclosed herein. The particular sequence of suchexecutable instructions or associated data structures represent examplesof corresponding acts for implementing the functions described in suchsteps.

Embodiments may be practiced in a networked environment using logicalconnections to one or more remote computers having processors. Logicalconnections may include a local area network (LAN) and a wide areanetwork (WAN) that are presented here by way of example and notlimitation. Such networking environments are commonplace in office-wideor enterprise-wide computer networks, intranets and the internet and mayuse a wide variety of different communication protocols. Those skilledin the art will appreciate that such network computing environments willtypically encompass many types of computer system configurations,including personal computers, hand-held devices, multiprocessor systems,microprocessor-based or programmable consumer electronics, network PCs,minicomputers, mainframe computers, and the like.

Embodiments may also be practiced in distributed computing environmentswhere tasks are performed by local and remote processing devices thatare linked (either by hardwired links, wireless links, or by acombination of hardwired or wireless links) through a communicationnetwork. In a distributed computing environment, program modules may belocated in both local and remote memory storage devices.

In accordance with an embodiment, FIG. 4 illustrates a method 100, whichmay be used for predicting a fault in an air-conditioning pack 22 of theair-conditioning system 10; such a predicted fault may include apredicted failure or where the level of the fault increases to where thesystem fails. The method 100 begins at 102 by transmitting from one ormore sensors 32 data related to the air-conditioning pack 22. Morespecifically, data may be transmitted from one or more sensors 32outputting data related to temperatures, pressures or flow rates, valvepositions, actuator positions, etc. for components of theair-conditioning packs 22 and their associated controllers 78. This mayinclude sequentially and/or simultaneously transmitting data from one ormore of the sensors 32. The transmitted data may be received by anysuitable device including a database or the controller 34 and/or thecontroller 60.

The transmitted data may be related to the pre-flight or the cruisesegments of the flight. More specifically, the transmitted data may besensor output(s) from the pre-flight, the cruise, climb, idle, descent,or post-flight. In an embodiment, the transmitted data may be for anynumber of segments including both the pre-flight and the cruise. Theterm pre-flight as used herein indicates any time until the wheels arelifted for flight, including taxiing of the aircraft 8, and may morespecifically include the time from when one or more engines have startedand the doors are closed until start of the takeoff roll. The termpost-flight as used herein indicates a time after the aircraft lands,including taxiing of the aircraft 8, and may more specifically includethe time after braking is complete and before the main engine is shutdown or the parking brake is set. In an embodiment, additional standardparameters, recorded by onboard systems, may be transmitted, such asaltitude and air or ground speed, such that the controller may determinewhen the aircraft 8 is in pre-flight and/or cruise. While thetransmitted data may be related to pre-flight or cruise, the data may betransmitted during any number of different phases of flight of theaircraft 8 or after the aircraft 8 has completed the flight. Forexample, sensor output may be transmitted once per flight, multipletimes per flight, or after the flight. It will be understood that thetransmitted data, including any sensor output, may include time seriesdata (eg. 1 Hz), aggregates, computed values, etc.

The transmitting of data at 102 may define sensor output(s) relevant toone or more characteristics of the air-conditioning pack 22. In anembodiment, the sensor output(s) may include raw data from which avariety of other information may be derived or otherwise extracted todefine the sensor output. It will be understood that regardless ofwhether the sensor output is received directly or derived from receivedoutput, the output may still be considered sensor output. For example,the sensor output may be aggregated over time to define aggregatedsensor data. Aggregating the transmitted sensor output over time mayinclude aggregating the transmitted sensor output over multiple phasesof flight and/or over multiple flights. Such aggregated sensor data mayinclude a median value, a maximum value, a minimum value, etc. Suchaggregated sensor data may be reset after a maintenance event.

At 104, the transmitted data may be compared to a predeterminedthreshold for the transmitted data. The predetermined threshold may beany suitable predetermined threshold related to the transmitted dataincluding that the predetermined threshold may be a temperature value, apressure value, an acceptable valve or actuator position range, etc. Thepredetermined threshold for the transmitted data may also include ahistorical predetermined threshold for the sensor output including forexample historical data related to the air-conditioning system of theaircraft or historical data for multiple other aircraft. Thus, theoutput signal may be compared to results obtained from previous flightsfor the same aircraft and against the whole fleet of aircraft.Furthermore, the predetermined threshold for the sensor output mayinclude a value that has been determined during operation.Alternatively, the predetermined thresholds may be stored in one of thedatabase(s) as described above.

In this manner, the sensor output may be compared to a predeterminedthreshold for the sensor output. Any suitable comparison may be made.For example, the comparison may include determining a difference betweenthe sensor output and the predetermined threshold. By way ofnon-limiting example, the comparison may include comparing a recentsignal output to a historic value. Comparisons may be made on a perflight basis or the data may be processed over a series of flights.Comparisons may further measure a change in correlation between twoparameters including where the correlation exceeds a given threshold.For example, in the instance where the transmitted data may beindicative of temperatures, pressures, valve and actuator positions ofthe air-conditioning pack 22 during the pre-flight and/or the cruise,the comparing may include comparing the temperatures, pressures, andpositions to corresponding predetermined thresholds. In the case wheremedian values are calculated for the transmitted data, the comparing at104 may include comparing the median value to the predeterminedthreshold. Further still when minimums and maximums for the transmitteddata may be determined, the comparing at 104 may include comparing theminimums and/or maximums to the predetermined thresholds. In anembodiment, multiple comparisons may be made at 104. For example, onetype of sensor data may be transmitted multiple times and thecomparisons may compare the data to a predetermined threshold such as acontrol limit.

At 106, a fault in the air-conditioning pack 22 may be predicted basedon the comparison(s) at 104. For example, a fault in theair-conditioning pack 22 of the air-conditioning system 10 may bepredicted when the comparison indicates that the sensor data satisfies apredetermined threshold. The term “satisfies” the threshold is usedherein to mean that the variation comparison satisfies the predeterminedthreshold, such as being equal to, less than, or greater than thethreshold value. It will be understood that such a determination mayeasily be altered to be satisfied by a positive/negative comparison or atrue/false comparison. For example, a less than threshold value caneasily be satisfied by applying a greater than test when the data isnumerically inverted.

Any number of faults in the air-conditioning pack 22 of theair-conditioning system 10 may be determined. By way of non-limitingexample, a fault may be determined with a heat exchanger of theair-conditioning pack 22. More specifically, it has been determined thata fault of a heat exchanger of the air-conditioning pack 22 may bepredicted when the comparisons indicate a pack compressor outlettemperature is rising towards a control limit. More specifically, it hasbeen determined that as the heat exchanger loses effectiveness, thecompressor outlet temperature of the air-conditioning pack 22 may risetowards a limit of 180° C.

Furthermore, as degradation continues, the ram air inlet flap positionmay be moved towards a forty percent open position during cruise to tryand increase cooling flow through the heat exchanger. On the ground, theflap is always maintained at one hundred percent, so this change inposition is not observed from data transmissions related to when theaircraft is on the ground. Once the compressor outlet temperature of theair-conditioning pack 22 may no longer be maintained by ram airflow, themedian pack flow may be observed to reduce below the nominal 0.45 kg/sduring both pre-flight and cruise. Furthermore, downstream temperatures,including the water extractor and pack outlet, may continue to rise. Toensure correct diagnosis of such heat exchanger issues, other featuresmay be monitored to ensure that they are within the normal range and notthe cause of the observed behavior. For example, additional featuresincluding bleed air temperature, bleed air pressure, bypass valveposition, and outside air temperature may be monitored and a fault maybe predicted with the heat exchanger when it is determined that theadditional features are within normal ranges.

Time periods for prediction of such a fault depend on the root cause,but for general degradation through accumulation of dirt etc., thedegradation can typically be identified six weeks prior to significantperformance impact and the state of degradation can be tracked throughthe various stages of increased temperatures, opening ram air flap, anddecreased pack flow allowing the severity of the issue to be known andprioritized accordingly.

Sensor faults may also be determined by determining a high number of outof range readings. It will be understood that any number of faults maybe predicted based on any number of comparisons so long as the relevantdata is obtained, appropriate comparisons are made, etc. Thesecomparisons may also be used to provide information relating to theseverity of the fault.

In this manner, the transmitted data may undergo statistical analysis inrelation to themselves and to other parameters/features and thisinformation may be used to determine impending faults and/or degradationand provide associated information such as severity and prognosticinformation by highlighting an impending failure of a particularcomponent. It will be understood that any suitable controller orcomputer may perform one or more portions of the method 100. Forexample, the controller of the aircraft compares the transmitted data,predicts the fault, and provides the indication. The controller mayutilize an algorithm to predict the fault. In implementation, thepredetermined thresholds and comparisons may be converted to analgorithm to predict faults in the air-conditioning pack 22 of theair-conditioning system 10. Such an algorithm may be converted to acomputer program comprising a set of executable instructions, which maybe executed by the controller 50 and/or the controller 60. Various otherparameters recorded by onboard systems such as altitude, speed, etc. mayalso be utilized by such a computer program to predict faults in theair-conditioning pack 22 of the air-conditioning system 10.Alternatively, the computer program may include a model, which may beused to predict faults in the air-conditioning pack 22.

At 108, the controller 50 and/or the controller 60 may provide anindication of the fault in the air-conditioning pack 22 predicted at106. The indication may be provided in any suitable manner at anysuitable location including in the cockpit 16 and at the ground system62. For example, the indication may be provided on a primary flightdisplay (PFD) in a cockpit 16 of the aircraft 8. If the controller 34ran the program, then the indication may be provided on the aircraft 8and/or may be uploaded to the ground system 62. Alternatively, if thecontroller 60 ran the program, then the indication may be uploaded orotherwise relayed to the aircraft 8. Alternatively, the indication maybe relayed such that it may be provided at another location such as anairline control or flight operations department.

It will be understood that the method of predicting a fault in anair-conditioning pack 22 is flexible and the method illustrated ismerely for illustrative purposes. For example, the sequence of stepsdepicted is for illustrative purposes only, and is not meant to limitthe method 100 in any way, as it is understood that the steps mayproceed in a different logical order or additional or intervening stepsmay be included without detracting from embodiments. By way of furtherexample, the transmitted data may include data from a plurality offlights, including the pre-flight and/or cruise portions of suchplurality of flights. In such an instance, comparing the transmitteddata may include comparing the data from the plurality of flights withrelated predetermined threshold(s). In this manner, multiple comparisonsmay be made utilizing the data for the plurality of flights. Further,predicting the fault may include predicting the fault when thecomparisons indicate the predetermined thresholds are satisfied apredetermined number of times and/or over a predetermined number offlights. Further, the predicted fault may be based on derived data suchas medians, minima, maximum values, standard deviations, counts above orbelow thresholds, change of state, correlations, etc. that may becalculated per phases of the flight of the aircraft.

Potentially beneficial effects of the above-described embodimentsinclude that data gathered by the aircraft may be utilized to predict afault in the air-conditioning system or subsystems thereof. This allowssuch predicted faults to be corrected before they occur. Currently thereis no manner to predict fault in the air-conditioning system orsubsystems thereof and unanticipated issues occurring during aircraftusage or even known issues, which require unplanned maintenance actions,lead to potential operational impacts for an airline. Theabove-described embodiments enable reduction of operational impacts,including a reduction in delays for passengers and in the level ofunscheduled maintenance required as a result of air-conditioning systemfaults. The above-described embodiments also help with planning ofscheduled maintenance due to prognostic information supplied. Theabove-described embodiments allow for automatic predicting and alertingto users of faults. The above-embodiments allow accurate predictions tobe made regarding fault in the air-conditioning system of subsystemsthereof. By predicting such problems, sufficient time may be allowed tomake repairs before such faults occur. This allows for cost savings byreducing maintenance cost, rescheduling cost, and minimizing operationalimpacts including minimizing the time aircraft are grounded.

This written description uses examples to disclose the embodiments,including the best mode, and also to enable any person skilled in theart to practice the embodiments, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the application is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims.

What is claimed is:
 1. A method of predicting a fault in anair-conditioning pack of an aircraft, wherein the air-conditioning packincludes one or more sensors outputting data related to air-conditioningpack temperature, air-conditioning pack pressure, or air-conditioningpack valve or actuator position, the method comprising: transmittingdata, output from at least one of the sensors, wherein the sensors areoperably coupled to the air-conditioning pack; comparing, by acontroller, the transmitted data to a predetermined threshold;predicting a fault in the air-conditioning pack based on the comparison;and providing an indication of the predicted fault.
 2. The method ofclaim 1, wherein transmitting the data comprises transmitting datarelated to a pre-flight and a cruise segment of a flight.
 3. The methodof claim 2, wherein transmitting the data comprises transmitting datafrom a plurality of flights.
 4. The method of claim 1, whereintransmitting the data comprises transmitting data from a plurality offlights.
 5. The method of claim 4, wherein comparing the transmitteddata comprises comparing the data from the plurality of flights with theat least one predetermined threshold.
 6. The method of claim 5, whereinpredicting the fault comprises predicting the fault when comparisonsindicate the predetermined thresholds are satisfied over multipleflights.
 7. The method of claim 1, wherein a controller of the aircraftcompares the transmitted data, predicts the fault, and provides theindication of the predicted fault.
 8. The method of claim 7, wherein thecontroller utilizes an algorithm to predict the fault.
 9. The method ofclaim 1, wherein the transmitted data is indicative of temperatures,pressures, valve positions, and actuator positions of theair-conditioning pack.
 10. The method of claim 9, wherein the comparingcomprises comparing the temperatures, pressures, and positions tocorresponding predetermined thresholds.
 11. The method of claim 10,further comprising calculating median values for the transmitted data.12. The method of claim 10, further comprising calculating minimums andmaximums for the transmitted data.
 13. The method of claim 9, furthercomprising calculating median values for the transmitted data.
 14. Themethod of claim 13, wherein the comparison comprises comparing themedian value to the predetermined threshold.
 15. The method of claim 14,further comprising calculating minimums and maximums for the transmitteddata.
 16. The method of claim 13, further comprising calculatingminimums and maximums for the transmitted data.
 17. The method of claim9, further comprising calculating minimums and maximums for thetransmitted data.
 18. The method of claim 17, wherein the comparisoncomprises comparing the minimums or maximums to the predeterminedthresholds.
 19. The method of claim 1, further comprising monitoring,with one or more sensors, additional features including bleed airtemperature, bleed air pressure, bypass valve position, and outside airtemperature.
 20. The method of claim 19, wherein the fault is predictedwith a heat exchanger of the air-conditioning pack when it is determinedthe additional features are within normal ranges.